Conventionally, engineers have developed technologies of efficiently delivering content data such as moving images. For example, PLT 1 discloses an interconversion method of multimedia data, which achieves efficient interconversion of multimedia data using multimedia pacing in a distributed data processing system. Specifically, a plurality of receiving stations are each designed to transmit a multimedia pacing request to a transmitting station in intervals of setting times via negotiation during a multimedia communication session. Herein, the multimedia pacing request includes an availability of a currently stored position of multimedia data in a receiving station, the information concerning the remaining time of minimum data at the stored position of a receiving station, and the information concerning interconversion of multimedia data. Then, the transmitting station assigns various priorities for data transmission to a plurality of receiving stations in an order reflecting a data format (i.e. multimedia data or non-multimedia data) and information of a multimedia pacing request concerning the remaining time of minimum data at each receiving station.
PLT 2 discloses a streaming method. Herein, a terminal determines a target value of streams (S_target), which should be stored in a buffer thereof depending on its own buffer capacity and a network transmission capability. In addition, the terminal arbitrarily writes head data of each stream into its own buffer within a range not exceeding a value that is obtained by dividing the buffer capacity by the transmission capability and then the terminal reads the head data so as to determine a delay time (T_delay) before the timing to start reproduction. The terminal notifies a server of a target value and a delay time. According to the notification by the terminal, the server controls transmission speed such that the buffer occupancy (Sum) of the terminal can be maintained in the neighborhood of the target value without exceeding the target value. Thus, it is possible to prevent failures in streaming reproduction irrespective of different buffer capacities of terminals depending on their types and irrespective of variations of network transmission capabilities, and therefore it is possible to reduce both the number of times concerning the occurrence of failures in streaming reproduction and the wait time of cueing.
PLT 3 discloses a data transmission method, which selectively controls a switching unit, connected between an input port unit having multiple input ports and an output window unit having multiple buffers, depending on the data stored condition for each of multiple buffers, stores data from multiple input ports on the vacant buffer among multiple buffers, and then transmits data, read from multiple buffers, in a time-division multiplexing manner. Thus, it is possible to reduce a possibility that input data will be destroyed due to overflowing or stagnation of processing in buffers, and therefore it is possible to reduce a possibility that the transmitting order of multisystem data will be changed. Herein, it is unnecessary to identify the header of data which may enter into the vacant buffer from each input port, and therefore it is possible to reduce delays without generating any buffer area useless for each output port and without the need of complex processing.
PLT 4 discloses a moving image delivery system, wherein a moving image delivery device changes a transmission rate of moving images with a predetermined bit rate based on an available bandwidth measured by a moving image playback device. Thus, it is possible to obtain good image quality in delivering moving images through networks undergoing significant fluctuations of bandwidths such as wireless packet networks.
PLT 5 discloses a wireless communication device. Specifically, a mobile phone includes a communication part for wirelessly transmitting data, an ECN (Explicit Congestion Notification) controller that, upon detecting network congestion, reduces a transmission window size, used for congestion avoidance, to be smaller than the foregoing one before the detection of congestion and then gradually increases the transmission window size, a token controller that sets a congestion avoidance mode during congestion avoidance or a normal node except for congestion avoidance, and a storage unit that stores a first value representing the transmission window size at the detection of congestion. Upon detecting congestion, the ECN controller notifies the token controller of an event to start congestion avoidance. When the transmission window size is changed to a second value specified based on the first value after the detection of congestion, the ECN controller notifies the token controller of an event to complete congestion avoidance. This guarantees the transition from the processing during congestion avoidance to the processing during the release of congestion avoidance at appropriate timing.